Explicating the neurobiological basis of cognitive functions such as visual short term memory has been a long standing goal of scientific research because it is essential for understanding normal cognitive functions and treating brain disorders that can devastate the ability to think and act. The proposed experiments will investigate the role of two brain areas, the posterior parietal and the dorsolateral prefrontal cortex in cognitive functions, relying on a non-human primate model. We will comparatively investigate the single-neuron and population responses in these two areas, with respect to visual short-term memory capacity, the influence of each brain area to memory involved behavior, and their functional plasticity as a result of training in short term memory tasks. These studies will help unveil the functional specialization of cortical areas involved in higher cognitive functions and offer insighs on normal cognitive processing as well as the consequences of brain injury and mental illness.